Diagnostic Method 1

Detect the malfunction depending on the average value of time necessary for λ to inverse the air fuel ratio from "Lean → Rich → Lean" to "Rich → Lean → Rich".

Fig 1: Sensor Output Timing Graph

Courtesy of SUBARU OF AMERICA, INC.

Judge as NG when the following conditions are established.

JUDGMENT VALUE

Malfunction Criteria	Threshold Value	DTC
Average value of time necessary for λ to inverse the air fuel ratio to Lean → Rich → Lean	> 100 ms	P015A and P015C
Average value of time necessary for λ to inverse the air fuel ratio to Rich → Lean → Rich	> 200 ms	P015B and P015D

Time Needed for Diagnosis: 90000 ms

Malfunction Indicator Light Illumination: Illuminates when malfunction occurs in 2 continuous driving cycles.